Prior Art PA0 Problems Which the Invention is to Solve PA0 Oxide-Based Catalyst PA0 Production of the Oxide-Based Catalyst PA0 Catalytic Hydrogenation of CO.sub.2 PA0 Working PA0 Effects of the Invention
In recent years, global warming due to accumulation of CO.sub.2 has become one of the serious environmental problems. It is an urgent necessity to reduce the amount of CO.sub.2 emitted or discharged. If carbon dioxide can be converted to a useful substance, for example methanol or a liquid fuel, for reuse as a resource, it will become possible to solve the global warming problem and at the same time achieve a saving of petroleum resources.
Various proposals have already been made for the production of methanol by catalytic hydrogenation of CO.sub.2 and studies on methanol synthesis catalysts therefor are in progress. Catalysts known for that purpose include oxide-based catalysts, metal catalysts and alloy catalysts. Among these, oxide-based catalysts are known to show good performance characteristics. The following oxide-based catalysts may be mentioned as typical examples: ZnO, ZrO.sub.2, Cu/ZnO, Cu/oxide, Cr.sub.2 O.sub.3 /ZnO, Cu/ZnO/oxide, Cu/ZnO/Al.sub.2 O.sub.3, ZnO/oxide, Cu/ZnO/Cr.sub.2 O.sub.3 /Al.sub.2 O.sub.3, etc.
A method is also known which comprises synthesizing a methanol-rich gas by catalytic hydrogenation of CO.sub.2 and at the same time synthesizing liquid hydrocarbons directly from the gaseous reaction mixture.
Thus, papers presented by the present inventors, namely Abstracts of papers for the 1984 Spring Meeting of the Chemical Society of Japan, vol. I, page 308, Abstracts of Papers for the 33rd Annual Meeting of the Japan Petroleum Institute, Special Lectures, and the 34th Meeting for Reading Research Papers, pages 71-74 and Preprints for the 66th Catalysis Forum (A) held by the Catalysis Society of Japan, page 118, disclose a process in which a first reactor and a second reactor are connected in series and in which, in the first reactor, a methanol-rich gas is produced from CO.sub.2 and H.sub.2 using a reduced CuO/ZnO/Cr.sub.2 O.sub.3 /Al.sub.2 O.sub.3 catalyst or a catalyst derived therefrom by modification with Pd, Rh, Ru or Ag, the gas from the first reactor is fed, as such, to the second reactor and, in the second reactor, said gas is contacted with an H-form Fe-silicate catalyst for conversion thereof into a liquid hydrocarbon-rich fraction.
Currently, this process is one of the most attractive ones since it has the possibility of achieving, by a single effort, both the reduction of CO.sub.2, which is regarded as the cause of global warming, and the saving of petroleum resources.
If, in the above-mentioned serial process reported by the present inventors, namely in the step of producing methanol from CO.sub.2 and H.sub.2 using a reduced CuO/ZnO/Cr.sub.2 O.sub.3 /Al.sub.2 O.sub.3 catalyst or a catalyst derived therefrom by modification with Pd, Rh, Ru or Ag, the conversion of CO.sub.2 and the selectivity toward methanol can be further increased, the industrial or commercial significance of said process will reach the stage of perfection.
It is an object of the invention, which has been completed under such circumstances, to provide a novel oxide-based catalyst capable of giving a high CO.sub.2 conversion and a high selectivity toward methanol in the catalytic hydrogenation of CO.sub.2, a method of producing said catalyst and a commercially advantageous method of catalytically hydrogenating CO.sub.2 using said catalyst.